Optical navigation sensors use a light source to illuminate a navigation surface to provide digital images for computing motion. However, as the spatial requirements of optical devices become more constrained, traditional light sources such as standard light-emitting diodes (LEDs) are replaced by smaller sources. In general, the available smaller sources have a lower power consumption, broader radiation patterns, and lower light intensity.
For optical mouse sensors, a typical imaged navigation surface is a surface such as a desktop or a mouse pad. Since this surface is to be lit in order to obtain an image, the light source should generate light with enough intensity to sufficiently illuminate the surface to obtain an adequate image for the generation of a navigation signal.
For a low profile illumination and sensor system with a total system height requirement of less than 5 mm, through-hole LED light sources can no longer be implemented in the system using conventional methods. One part of a solution to this spatial constraint is the replacement of the conventional LED with a low-profile LED, such as a Chip LED, Top LED, or a bare LED die as the light source. The result of replacing a conventional LED with the mentioned low-profile LED is that the radiation pattern of the low-profile LED has a lower light intensity due to the fact that the light is spread across a significantly wider angle. For example, the field of emitted light can be up to 160° at full angle. Such a large angle reduces power concentration and results in a lower light intensity. Due to this, it is difficult to collect the wide angle light, guide it properly, and emit the light with an intensity sufficient to obtain an adequate navigation image.